ESD-mat, should I ground it in the house?

[Calby]

(Please only people that know what there are talking about should answer, thanks.)

Hi everyone,
People are saying different things regarding this with ESD and it's driving me nuts.
Some things I do understand, but the thing that I can't figure out now is if I should connect the ESD-mat to my house grounding.
Some people says that it's not needed and that I should just connect the mat to the computer and to my wrist as I only need to have the same level (grounding) as the computer and therefore I don't need to connect it to my houses grounding.
An other people are telling me that I need to connect to my houses grouding because it wont work if I do it and my component are in danger for ESD.

So now I have connected it like this:
ESD-Mat to my computer (don't know if it's the best place to connect it in the computer, it's hard as it's a laptop)
ESD-Mat to my wrist troug ha ESD-wristband.

I'm putting my ESD-safe tools on the mat all the time before and during when I'm screwing in my laptop.
I put the component package in 30sec before I'm opening it so that it 'll have the same level of energi as the rest of the things.

Is this the right way to do it? Or should I also ground it in my houses grounding also?

 

[Mr Evil]

Imagine that you are charged up to a potential of 1kV relative to earth. You connect yourself and the computer together through the mat. Great! Now the computer is at the same potential as you, so you won't discharge into it. But now the computer is at 1kV relative to the earth, and might shock itself if it touches anything. In conclusion, connect the mat to earth before touching anything.

 

[Calby]

Imagine that you are charged up to a potential of 1kV relative to earth. You connect yourself and the computer together through the mat. Great! Now the computer is at the same potential as you, so you won't discharge into it. But now the computer is at 1kV relative to the earth, and might shock itself if it touches anything. In conclusion, connect the mat to earth before touching anything.

Ok, Can I just take a extension cord form a grounded power outlet and then take the crocodile clip from the mat and attache it to the grounding thing in the extension cord, see the picture it's in the circle what I mean.

Edit:
Now I'm getting paranoid, I did replace the RAM on my laptop without grounding the mat to earth, but the laptop works so it should not bee any danger but I hate when I'm not doing things right.

Do you know any good place to connect the mat to the laptop? As you can see in my picture above it's not good I think.
But I maybe not need to do it as the laptop are on the mat? Then it should get the same level as the rest of the things that are connected to the mat right?

 

[Mr Evil]

Connect the mat to whatever is convenient. The motherboard will be fine just sat on the mat. It's not a big deal if you don't take care to ground yourself unless you live somewhere very dry, or have a habit of dragging your feet across synthetic carpet, or like to stick balloons to your hair.

 

[Rayniac]

Connect the mat to whatever is convenient. The motherboard will be fine just sat on the mat. It's not a big deal if you don't take care to ground yourself unless you live somewhere very dry, or have a habit of dragging your feet across synthetic carpet, or like to stick balloons to your hair.

This. There is no need to be paranoid. As with everything, even in electronics people would have you buy things you don't actually need.

 

[Murloc]

the easiest would be to just use a broken power cord and connect the ensemble of interconnected stuff to the house ground.
This way it's impossible that a potential difference is created between the system and the real ground.

I'm not sure about how much resistance towards ground there would be this way but you could also use the metal case of an appliance that is plugged in to create the connection.

 

[ch33zw1z]

In my training, ESD is not about grounding, it's about minimizing potential difference.

The mat doesn't need to be grounded, just hook the wrist strap up to it (while you're wearing it) and wait 10 seconds before touching anything on the mat.

 

[Red Squirrel]

Personally I would just ground it for good measure, as ground tends to be a common reference point for everything. I have an outlet box that has a metal plate and I tend to touch it to discharge myself and don't even bother with a wrist strap or antistatic mat. Suppose I should, but never had issues.

 

[Valantar]

Now, I'm not an electrical engineer or anything like that, but I have built a handful of desktops and torn down (and rebuilt) more laptops for fun than any sane person should. Dumpster diving will do that to you.

Anyhow, I've entirely torn down and rebuilt laptops without any kind of ESD protection whatsoever (behind the counter of a shop I used to work at, after raiding the electronics recycling bin in the shopping centre basement), with no issues whatsoever. In fact, I have two laptops that I did that to still, and both work fine. And by tearing down I mean down to the bare PCBs, removing old thermal paste, cleaning off dust and in general handling the motherboards quite a lot.

I've also built (and torn down/rebuilt) PCs wearing woolen socks (my apartment has very cold floors!), sitting on a rolling office chair, and all kinds of other ESD no-nos. In a room that also houses a treadmill, by the way. At home, I ground myself sporadically while working by touching either a plugged-in PC/power supply or the heating radiators on the wall. I did get a wristband at one point, but ended up not using it due to it being too short to work comfortably (I didn't have a suitable grounded extension cord at the time).

Now, I'm not arguing that all anti-ESD measures are entirely unnecessary. Heck, I even bought an Alphacool Eisplateau ESD-safe workmat for my upcoming upgrade - both to mitigate the hassle of using a wrist strap and to protect the table I'll be building on. But a good rule of thumb is this: don't be careless, and you'll be fine. And, to be extra careful, ground yourself to ground from time to time. While "grounding" yourself and the mat to the part in question will minimize potential voltage differences between you and the part, as Mr Evil said, it won't change a thing relative to anything else - and the act of connecting either yourself or the part might very well cause a shock to begin with. Ground the mat first.

 

[Red Squirrel]

I do wonder if maybe today's parts are less sensitive to ESD. I think normally you are fine, as long as you're not actually shooting blue lightening out of your fingers every time you touch something. I had an interesting ESD incident in my house a while back though. I was vacuuming up a very fine powder with the central vac and the hose is made of plastic. This was making all my hair stand still and I could actually feel electrical discharge from my arms and hands. I was near one of my temperature sensors which goes back to my home automation system. After I was done I noticed that the sensor was reading 0C and the furnace had started. After some troubleshooting it seemed the sensor itself was seized. It was also very hot to the touch. I had to cut power to the sensor itself, reset the microcontroller then plug everything back in and it was good to go. Almost like the ESD flipped some bits and just locked it up. Did not damage it thankfully. I need to redo that whole system though, ESD or any kind of stray electrical was not taken into account in the design. Idealy, each sensor should be on an isolated DC circuit and have over voltage protection. I can probably create isolation using a transformer and a bunch of individual windings for separate circuits. (PWM then smooth it out)

 

[Rayniac]

I do wonder if maybe today's parts are less sensitive to ESD. I think normally you are fine, as long as you're not actually shooting blue lightening out of your fingers every time you touch something. I had an interesting ESD incident in my house a while back though. I was vacuuming up a very fine powder with the central vac and the hose is made of plastic. This was making all my hair stand still and I could actually feel electrical discharge from my arms and hands. I was near one of my temperature sensors which goes back to my home automation system. After I was done I noticed that the sensor was reading 0C and the furnace had started. After some troubleshooting it seemed the sensor itself was seized. It was also very hot to the touch. I had to cut power to the sensor itself, reset the microcontroller then plug everything back in and it was good to go. Almost like the ESD flipped some bits and just locked it up. Did not damage it thankfully. I need to redo that whole system though, ESD or any kind of stray electrical was not taken into account in the design. Idealy, each sensor should be on an isolated DC circuit and have over voltage protection. I can probably create isolation using a transformer and a bunch of individual windings for separate circuits. (PWM then smooth it out)

Are you saying that it was the interaction of the powder and the hose that caused the electrical charge to build up? What were you vacuuming exactly?

 

[hal2kilo]

It's funny, I'm a non degreed Senior Engineer (field engineer). We have to have ESD training every year or 2. When I go to our System Test facility at our home office the damn degreed Engineers barely use any ESD practices. The problem is that the possibility is there, especially in dry climates. Me personally with my own gear at home, I make sure to touch something grounded to earth and touch the case at the same time and that's about it. For safety reasons, you are supposed the have a 1 Meg resistance between you and the common ground.

 

[ra1nman]

If you're really that concerned about the mat, just ground it to the screw on the closest outlet cover.

 

[MrDudeMan]

I've designed ESD protection clamps, diodes, etc. and I rarely use an ESD strap. The reason is because the failures aren't likely to be instantaneous or catastrophic, so it's not worth the hassle unless the replacement cost of the DUT is non-trivial. When I'm messing with a server that has $800k worth of custom electronics, I wear what can only be described as a full body ESD condom, but for a motherboard in a PC? Not worth the hassle.

Minimizing the potential between yourself and the DUT is good, but that's not the only piece of the puzzle. Current flow can be just as damaging and that can happen with little to no voltage difference. Some devices, such as 22 nm transistors, can become permanently inoperable after a single discharge above 2.0 V while some can tolerate 10 V or 100 V dozens of times. The failure mechanism is usually like this: working perfectly -> occasional hiccups -> frequent problems -> no longer operational. Of course, it completely depends on the device, environment, and various other things, but that's the general idea.

Balancing the charge between your body and the DUT by connecting to a mat and waiting a few seconds isn't a bad idea, but I personally wouldn't bother unless the mat is also connected to earth ground. The theory is you shouldn't need earth ground because your body isn't going to violently charge share with the DUT due to wearing a strap that is electrically connected to the mat, but in practice it's entirely possible to zap something with another object that isn't conductive and isn't on the mat. I coat the floor of my workshop with conductive epoxy, which then conducts through a ground rod into the earth. All of my ESD mats connect to the same ground rod and I've never had a single loss in my lab due to ESD as a result.

In your situation, you'll be fine without upgrading your ESD setup as long as you aren't being intentionally stupid or negligent. With that said, you have to understand the nature of an ESD mat. It doesn't magically dissipate energy. If you walk around with an ESD mat connected to your body and you purposely accumulate charge by rubbing your socks on the carpet, you could still damage a component sitting on the mat. A mat that isn't grounded is electrically floating and, therefore, susceptible to discharge. The bottom line is if you're worried about it, ground the mat. It will take a few seconds and then it's done.

 

[Red Squirrel]

Are you saying that it was the interaction of the powder and the hose that caused the electrical charge to build up? What were you vacuuming exactly?

Baking soda. Long story short my cat pukes a lot, and I was experimenting with different ways to kill the smell, so I dumped a whole box of it on the couch and let it sit for a few days. Then I vacuumed it up.

If ever I accidentally vacuum up a vinegar packet I'm probably getting an explosion.

 

[Rayniac]

Huh. I never thought of baking soda as a particularily static material. I'll have to test that sometime

 

[Red Squirrel]

Huh. I never thought of baking soda as a particularily static material. I'll have to test that sometime

Yeah I thought it was interesting too. But I guess it makes sense, it's a very dry powder and it was rushing fast through a plastic hose. The plastic hose probably played a big role too, maybe even the surface of the couch.

 

[MrDudeMan]

I do wonder if maybe today's parts are less sensitive to ESD. I think normally you are fine, as long as you're not actually shooting blue lightening out of your fingers every time you touch something. I had an interesting ESD incident in my house a while back though. I was vacuuming up a very fine powder with the central vac and the hose is made of plastic. This was making all my hair stand still and I could actually feel electrical discharge from my arms and hands. I was near one of my temperature sensors which goes back to my home automation system. After I was done I noticed that the sensor was reading 0C and the furnace had started. After some troubleshooting it seemed the sensor itself was seized. It was also very hot to the touch. I had to cut power to the sensor itself, reset the microcontroller then plug everything back in and it was good to go. Almost like the ESD flipped some bits and just locked it up. Did not damage it thankfully. I need to redo that whole system though, ESD or any kind of stray electrical was not taken into account in the design. Idealy, each sensor should be on an isolated DC circuit and have over voltage protection. I can probably create isolation using a transformer and a bunch of individual windings for separate circuits. (PWM then smooth it out)

I missed this on the first pass through the thread. What you described is almost certainly latch-up, which usually occurs in a PNPN junction. If you manage to get a device to latch up, usually as part of the substrate in a CMOS device such as the microcontroller you described, a power cycle is required to clear the fault assuming it doesn't release its magic smoke first. Latch-up is bad news and a lot of design effort is spent trying to avoid it, but ESD discharges are capable of causing it as are many other things. Incorrect power supply sequencing is also to blame sometimes. In a nutshell, the dopants in a substrate are used to create transistors obviously, but they also create diodes between more components than you actually want most of the time. In some situations, you can have what is effectively a PNP and NPN transistor right next to each other that can cause each other to conduct as long as some current flows in a specific direction and circumstance. When you get into that state, the transistors will continue to keep each other saturated until you turn the power off, which would be a latch-up condition. It can manifest other ways as well, but you almost always see that behavior.

 

[Valantar]

Yeah I thought it was interesting too. But I guess it makes sense, it's a very dry powder and it was rushing fast through a plastic hose. The plastic hose probably played a big role too, maybe even the surface of the couch.

In my mind what you're describing is pretty much an ideal scenario for generating static electricity, as such I fail to see how people find it surprising... Forcing a loose cloud of a dry, powdery substance through a ridged tube of soft plastic at high speed and with lots of turbulence - how would that not generate a lot of static?

 

[Rayniac]

I didn't expect baking soda to do that because it's a salt. Usually we see static charges generated from the friction of some sort of plastic and organig fibers like human hair or wool socks. But then again I'm not aware of the mechanics involved in static electricity generation when it comes to the atomic scale.

 

[who?]

Boil a lot of water so that the house is full of humidity. This will kill the risk of static.

 

[ch33zw1z]

Boil a lot of water so that the house is full of humidity. This will kill the risk of static.

Not sure if serious. Seems like a waste of water and recipe for mold lol.

Just read my first post in the thread.